1. Field of the Invention
The invention relates to a cutter assembly for a mowing apparatus. The invention is more particularly concerned with a cutter assembly comprising a plurality of sickle guards arranged side by side, each sickle guard having at least one guard, each guard having a guard body and being releasably fixed at least with its guard body to a cutter bar, a ledger surface on each guard body having lateral guard body cutting edges, knife sections secured to a reciprocable knife back, each knife section having a bottom face, facing said ledger surface, and lateral facets terminating in knife section cutting edges, rigid hold-down arms fixedly mounted to said cutter bar spaced from each other in the longitudinal direction of said cutter bar, each hold-down arm having a front part extending above upper faces of said knife sections.
2. Description of the Prior Art
In one known cutter assembly of this type (GB-Patent 1,155,464) the front parts of the hold-down arms are normally positioned at a distance above the knife sections. It is only during an upward movement of the knife sections that the latter will enter into sliding contact with the front parts; (page 2, lines 104 to 109). The knife sections can rise above the ledger surfaces of the guard bodies by said distance. This will reduce the cutting quality. The knife section cutting edges of each second knife section are positioned upwards, which will lead to increased wear of the hold-down arms.
Similar known cutter assemblies having the same disadvantages are disclosed in U.S. Pat. Nos. 1,945,301 and 2,484,652, FIG. 5.
From U.S. Pat. No. 3,455,093 it is known per se to raise and lower the hold-down arm about a horizontal hinge pin and to press its front part via a replaceable anti-friction rub strip into constant contact with the upper faces of the knife sections. This is achieved through a compression spring which rests on the one hand against a rearward extension of the hold-down arm and on the other hand on a base plate which carries said hinge pin at its forward end. The base plate is screwed to the cutter bar. The pressing force of the rub strip can be adjusted by a screw which is arranged concentrically with said compression spring.
From DE Offenlegungsschrift 1 507 170 several proposals are known per se to resiliently or through screw adjustment raise or lower a hold-down arm relative to the knife sections.
Such screw adjustments are also known per se from U.S. Pat. No. 3,722,196, DE Offenlegungsschrift 1 816 316 and DE 2 343 491 A1.
From FR 2 546 367 A1 it is known per se to use hold-down arms in the form of upper double guards. These upper double guards are supported by the cutter bar with a fixed extension behind the guard mounting screws and with an adjusting screw in front of the guard mounting screws. The hold-down arms may be adjusted relative to the knife sections by concerted, complementary adjustment of the guard mounting screws and the adjusting screws.